This invention relates to a mould for casting a standard Magnesium ingot. Further, this invention relates to an automated method of casting standard Magnesium ingots using the mould of the present invention.
It is known to cast ingots using moulds into which molten metal is poured. In the case of Magnesium, a standard 25 or 26 pound ingot is made by typically using a trough type mould having an open top which is approximately 28xe2x80x3 longxc3x976.5xe2x80x3 widexc3x972.5xe2x80x3 deep. The term xe2x80x9cstandardxe2x80x9d relates both to the size and weight of the ingot and ultimately depends on the type of equipment used to cast magnesium parts. It can be seen that this mould exposes a surface area of approximately 182 sq. inches of the molten metal to the surrounding air. In the case of Magnesium this is important since the molten metal reacts with air causing it to burn at the exposed surface.
In order to prevent burning, an oxidizing agent such as SO2 (sulphur dioxide) or SF6 (sulphur hexaflouride) is used to create an oxide layer at the exposed surface area of the molten metal. The oxide layer of surface skin thereby formed prevents the molten Magnesium from reacting with air and burning. The disadvantage of using these gases relates to cost, and the environmental hazards and health risks they pose. While there is nothing wrong with the prior art moulds in terms of the Magnesium ingot produced, the drawback lies with the requirement and need to use large quantities of these environmentally toxic gases.
It is an object of the present invention to provide a mould for casting a better quality Magnesium ingot which significantly reduces the need to use oxidizing agents or masking gases such as Argon.
It is a further object of the invention to automate the casting of Magnesium ingots which method is greatly facilitated by the use of a mould made in accordance with this invention.
These objects are achieved by providing a vertical Magnesium mould for casting a standard ingot comprising an internally tapered chamber having an open top and a closure at the bottom thereof. The mould accordingly has a small opening at its top to minimize the surface area of the molten Magnesium in the mould chamber which is exposed to air.
Furthermore, the mould of the present invention is preferably built with cooling fins around its periphery to better dissipate the heat from the molten metal and thus achieve more rapid cooling of the Magnesium in the mould. As well, the mould walls which define the chamber are tapered downwardly and outwardly to facilitate the removal of the Magnesium ingot.
Yet further, the cross-section of the mould chamber may be varied to permit various handling or stacking strategies for the ingot, as for example; circular, substantially rectangular, or xe2x80x98bow tiexe2x80x99cross-sections as described elsewhere in this specification.
The mould of the present invention may be used as part of a process to recycle Magnesium scrap into ingots. The mould lends itself to automation, and is adapted for inclusion as part of an automated system for efficiently producing Magnesium ingots. According to this method, a plurality of moulds each having suitable attachment means are attached to the belt of a conveyance system at uniform distances. The belt of the conveyance system forms a complete loop such that each mould during one full cycle is successively carried to various automated stations involved in the production of the ingot including; evaporation chamber, pouring chamber, cooling chamber, and ingot station where the finished ingot is mechanically removed.